hkdf.h File Reference

RFC 5869 HKDF over HMAC-SHA-256, plus the TLS 1.3 / QUIC HKDF-Expand-Label construction (RFC 8446 7.1, RFC 9001 5.1). More...

#include "crypto/symmetric/hash/hash/hmac.h"

Go to the source code of this file.

Data Structures
struct	hkdf_label
	HkdfLabel inputs (RFC 8446 7.1): the label (without the "tls13 " prefix) and the context (may be empty: {0, 0}). More...

Macros
#define	HKDF_PRK   SHA256_DIGEST
	pseudorandom key length
#define	HKDF_PRK_384   SHA384_DIGEST
	pseudorandom key length for the SHA-384 instantiation

Functions
void	hkdf_extract (wired_span salt, wired_span ikm, u8 prk[HKDF_PRK])
	prk = HKDF-Extract(salt, ikm).
int	hkdf_expand (const u8 prk[HKDF_PRK], wired_span info, wired_mspan okm)
	okm = HKDF-Expand(prk, info, okm.n).
int	hkdf_expand_label (const u8 prk[HKDF_PRK], const hkdf_label *l, wired_mspan okm)
	okm = HKDF-Expand-Label(prk, label, context, okm.n) with the "tls13 " prefix.
void	hkdf_extract_384 (wired_span salt, wired_span ikm, u8 prk[HKDF_PRK_384])
	prk = HKDF-Extract(salt, ikm) instantiated with HMAC-SHA-384 (RFC 5869 2.2, TLS_AES_256_GCM_SHA384).
int	hkdf_expand_384 (const u8 prk[HKDF_PRK_384], wired_span info, wired_mspan okm)
	okm = HKDF-Expand(prk, info, okm.n) instantiated with HMAC-SHA-384 (RFC 5869 2.3).
int	hkdf_expand_label_384 (const u8 prk[HKDF_PRK_384], const hkdf_label *l, wired_mspan okm)
	okm = HKDF-Expand-Label(prk, label, context, okm.n) with the "tls13 " prefix, instantiated with HMAC-SHA-384 (RFC 8446 7.1, RFC 9001 5.1).

Detailed Description

RFC 5869 HKDF over HMAC-SHA-256, plus the TLS 1.3 / QUIC HKDF-Expand-Label construction (RFC 8446 7.1, RFC 9001 5.1).

Function Documentation

hkdf_expand()

int hkdf_expand	(	const u8	prk[HKDF_PRK],
		wired_span	info,
		wired_mspan	okm )

okm = HKDF-Expand(prk, info, okm.n).

okm.n must be <= 255*32.

Parameters

prk	32-byte pseudorandom key from hkdf_extract()
info	context/application-specific info (may be empty)
okm	receives exactly okm.n bytes of output keying material

Returns

1 on success, 0 if the length is out of range.

hkdf_expand_384()

int hkdf_expand_384	(	const u8	prk[HKDF_PRK_384],
		wired_span	info,
		wired_mspan	okm )

okm = HKDF-Expand(prk, info, okm.n) instantiated with HMAC-SHA-384 (RFC 5869 2.3).

okm.n must be <= 255*48.

Parameters

prk	48-byte pseudorandom key from hkdf_extract_384()
info	context/application-specific info (may be empty)
okm	receives exactly okm.n bytes of output keying material

Returns

1 on success, 0 if the length is out of range.

hkdf_expand_label()

int hkdf_expand_label	(	const u8	prk[HKDF_PRK],
		const hkdf_label *	l,
		wired_mspan	okm )

okm = HKDF-Expand-Label(prk, label, context, okm.n) with the "tls13 " prefix.

Parameters

prk	32-byte pseudorandom key
l	label and context inputs (see hkdf_label)
okm	receives exactly okm.n bytes of output keying material

Returns

1 on success, 0 if the label/context/length do not fit.

hkdf_expand_label_384()

int hkdf_expand_label_384	(	const u8	prk[HKDF_PRK_384],
		const hkdf_label *	l,
		wired_mspan	okm )

okm = HKDF-Expand-Label(prk, label, context, okm.n) with the "tls13 " prefix, instantiated with HMAC-SHA-384 (RFC 8446 7.1, RFC 9001 5.1).

Parameters

prk	48-byte pseudorandom key
l	label and context inputs (see hkdf_label)
okm	receives exactly okm.n bytes of output keying material

Returns

1 on success, 0 if the label/context/length do not fit.

hkdf_extract()

void hkdf_extract	(	wired_span	salt,
		wired_span	ikm,
		u8	prk[HKDF_PRK] )

prk = HKDF-Extract(salt, ikm).

Parameters

salt	optional salt (may be empty)
ikm	input keying material
prk	receives the 32-byte pseudorandom key

hkdf_extract_384()

void hkdf_extract_384	(	wired_span	salt,
		wired_span	ikm,
		u8	prk[HKDF_PRK_384] )

prk = HKDF-Extract(salt, ikm) instantiated with HMAC-SHA-384 (RFC 5869 2.2, TLS_AES_256_GCM_SHA384).

Parameters

salt	optional salt (may be empty)
ikm	input keying material
prk	receives the 48-byte pseudorandom key